Zirconia nanoparticles/ferroelectric liquid crystal composites for ionic impurity-free memory applications

Abstract

We observed an ionic impurity-free memory effect using a zirconia nanoparticles (ZNPs)/ferroelectric liquid crystal (FLC) composite. The pure and ZNPs doped FLC cells have been analyzed by means of dielectric spectroscopy, polarizing optical microscopy and electrical resistance/conductivity measurements.The memory behavior in ZNPs/FLC composite was confirmed by dielectric dispersion, electrical, and optical studies, whereas dielectric loss spectra confirmed the disappearance of the low-frequency relaxation peak, which appears due to the presence of ionic impurities in FLC materials. The observed memory effect has been attributed to minimization of the depolarization field and ionic charges, whereas the reduction of ionic effects has been attributed to the strong adsorption of ionic impurities on the surface of ZNPs. The ZNPs dispersed in FLCs may play a role in trapping the impurity ions (minimize the depolarization fields) under applied voltage and cause a better memory effect in ZNPs doped FLC material. Moreover, the ion adsorption capability of ZNPs is found to be almost independent of temperature as the value of resistance did not change remarkably on increasing the temperature. The reduction of ionic impurities of FLCs by doping ZNPs did not show degradation over time, as we repeated the experiments on the same sample cells after many days and did not find ionic effects in the ZNPs doped FLC materials. These studies would be helpful to provide an idea for designing ionic impurity-free memory devices.

Formation of periodic domains and change in physical properties of paramagnetic copper doped ZnO nanoparticle dispersed ferroelectric liquid crystal system

“…FLCs have also proven their potential applicability in the tunable laser, diffraction grating, ionic impurity free memory devices, etc. [8][9][10].…”

Nano-Objects and Ions in Liquid Crystals: Ion Trapping Effect and Related Phenomena

“…According to [186,187], the applied electric field polarized the nanoparticle, and ions in liquid crystals were trapped at the surface of the polarized nano-dopant.…”

“…Electrical properties of liquid crystals doped with metal oxide nanoparticles were reported in many papers summarized in Table 4 [173][174][175][176][177][178][179][180][181][182][183][184][185][186][187][188][189][190]. [173,174].…”

Low-voltage electro-optical memory device based on NiO nanorods dispersed in a ferroelectric liquid crystal

“…Recently, it is seen that ZrO 2 NPs/FLC composites showed a non-volatile memory behavior due to adsorption of impurity ions on to the surface of NPs. 20 Apart from imparting the memory effect, dispersing the nano structures into the LCs have improved the molecular alignment, dielectric and electro-optical characteristics of the host material such as enhanced optical contrast, faster response time, low operational voltage etc. 16 Also, low power operating devices are highly appreciable since the saving of energy is equally important as that of production.…”

“…A variety of nano structured materials including metal nanoparticles (NPs), 19 metal oxide NPs, 20 ferroelectric NPs, 21 carbon nanotubes, 22 quantum dots 23 etc. have been used to improve the memory behavior of LCs.…”